The Evolution of US EPA Method 525
“DETERMINATION OF SEMIVOLATILE ORGANIC CHEMICALS IN DRINKING WATER BY SOLID PHASE EXTRACTION AND CAPILLARY COLUMN GAS CHROMATOGRAPHY/ MASS SPECTROMETRY (GC/MS)”
Initially published in 1988, Method 525 had two additional versions before the latest version, Method 525.3, was published in 2012. For brevity, we will provide the conclusion to the article first and then the main body.
The primary difference between Method 525.3 and the previous versions of Method 525 is that certain DVB products, but not all DVB products, can be used as extraction media. Allowed products, or their quality equivalents, are listed in Sections 6.9 through 6.13. The note quoted below is from Section 6 of Method 525.3.
*Note: Several brands of SDVB and modified SDVB media in cartridge format were evaluated during method development and did not provide satisfactory performance. Therefore, SDVB cartridges are not included in this method.*
UCT product ECUNI525, or equivalent, is the only product approved for use with ALL versions of EPA Method 525 since it is a C18 approved for Method 525.3.
The original method was titled “Determination Of Organic Compounds In Drinking Water By Liquid-Solid Extraction And Capillary Column Gas Chromatography/Mass Spectrometry” and was a bare bones method utilizing silica based C18 for what was described as Liquid-Solid Extraction.
Method 525.1 was published May 1991 and contained an expanded list of analytes and mentioned the use of C18 disks for extraction as well as refined options for calibration.
Method 525.2 was published in 1995, incorporating refinements based on advancements in analytical techniques. Method 525.2 expanded the list of target organic compounds and improved detection limits for certain pesticides and industrial pollutants. It incorporated more refined solid-phase extraction (SPE) techniques, making it more efficient for detecting semi-volatile organic compounds. Method 525.2 became the preferred method for drinking water analysis, ensuring compliance with Safe Drinking Water Act (SDWA) regulations.
Method 525.3 was published in February 2012. Besides providing more options for sample extraction, the method changed to safer sample preservation reagents. Method 525.2 used sodium sulfite and hydrochloric acid for sample preservation. Method 525.3 replaced these with powdered preservatives, which adjust the sample pH to 3.8, allowing for a wider range of analytes to be extracted in a single extraction. Other key improvements included:
- Using Single Ion Monitoring (SIM) to achieve lower Detection Limits (DL)
- Quantitation ions can be modified
- Easier DFTPP requirements – 525.3 does not require monitoring ions 51, 127, or 275
- Daily DFTPP check is no longer required
- Using matrix-matched calibration standards compensates for matrix enhancement.
- Adding the internal standard post-extraction provides a more accurate measure of overall extraction efficiency & analyte recovery, avoiding over or under compensation for recovery of compounds that differ in structure from the 525.2 extracted internal standards during quantitation.
